Module 5 Laboratory Flashcards
basic mechanism for contraction (3)
(1) electrical excitation of muscle cell
(2) excitation-contraction coupling
(3) sliding of muscle filaments or contraction
electrical potential difference across the muscle cell membrane equal to approximalely
-80mV
inside of the mebrane is negatively/postively charge
negatively
____ is stimulated either by direct electric shock or by the motor nerve that innervates the muscle
muscle cell
what diffuses into the cell that depolarizes the membrane and its polarity momentarily reverses
Na+
diffuses out of the cell membrane which repolarizes the membrane and establishes the more negative resting membrane potential
K+
rapid depolarization and repolarization of the membrane at the stimulated point
action potential
as action potentials are conducted along the muscle cell membrane, they stimulate a rise in the cytoplasmic concentration of what
Ca2+
Ca2+ comes from a system of intracellular tubules called the
sarcoplasmic reticulum
in the resting muscle, the absence of this calcium allows two (2) proteins to inhibit contraction
troponin
tropomyosin
as a result of electrical stimulation, Ca2+ is released into the cell and becomes attached to what protein
troponin
complex that have their inhibitory effect removed
troponin-tropomysin complex
the influx of what is said to couple electrical excitation to muscle contraction
calcium ions
oriented parallel to the long axis of the fiber within the muscle cell
fibrils
repeating subunits in each fibril
sarcomere
functional unit of contraction
sarcomere
thick filament
myosin
thin filament
actin
as the sarcomeres becomes shorter, the fibrils and thus the entire muscle cell shorten, resulting in ____
muscle contraction
skeletal muscles are stimulated to contract by which nerves
somatic motor nerves
neurotransmitter that is released when action potentials in the mother nerves elicit this response
acetlycholine
causes ca2+ to be released from the sarcoplasmic reticulum
electrical stimulation
produces an injury current that stimulates action potentials and subsequent muscle contractions when for example, a somatic nerve is pinched
damagee
secondary to nerve damage or to dysfunctions at the neuromuscular junctions
muscle degeneration
follows damage to the motor nerve pathay because proper muscular activity and resulting muscle tone are required for the health of the msucle
muscle degeneration
abnormal muscle weakness or fatigue wherein the antibodies secreted by the immune system block the muscle membrane receptors fo acetylcholine
myasthenia gravis
what muscle is directly stimulated
gastrocnemius
stimulus where the msucle respond with a contraction
threshold stimulus
another name for a muscle cel is called
myocyte
The electrical events in the muscle cell that stimulate contraction are known as
excitation-contraction coupling
. The basic repeating subunits of contraction within the muscle cell are known as
sarcomeres
Associated with the thin filaments within each skeletal muscle sarcomere are two inhibitory proteins known as
troponin
tropomyosin
- What substance couples electrical excitation to muscle contraction
calcium
s the least amount of nerve stimulation required to elicit a response from a specific group of muscle fibers, known as a motor unit. Smaller motor units linked with smaller, lower-threshold motor neurons are activated initially during muscle contraction, resulting in a low level of contractile strength. When more force is required, larger motor units with higher-threshold motor neurons are activated, which contributes to increased muscular contraction.
treshold
Explain why the threshold stimulus for producing a muscle twitch is lower when the sciatic nerve is stimulated than when the gastrocnemius muscle is stimulated directly.
Simply because the sciatic nerve innervates and stimulates a wider range of muscle fibers compared to the gastrocnemius muscle, alone. When electrical stimulation was applied to the sciatic nerve, it activated all the muscle fibers in the gastrocnemius muscle, on the other hand, the direct stimulation of the muscle only activated the muscle fibers in the immediate area of the electrode. This implies that a lower stimulus is needed to produce a muscle response (twitch) when the sciatic nerve is stimulated because it activates a larger number of muscle fibers.
long cylindrical structures that lie parallel to the muscle fiber
myofibrils
run the entire length of the muscle fiber
myofibrils
plasma membrane of the muscle fiber
sarcolemma
appearance of skeletal muscle is a result of repeating bands of the proteins actin and myosin that occur along the length of myofibrils
striated
myofibrils are composed of smaller structures called
myofilamnets
two main types of myofilaments
thick filaments (myosin)
thin filaments (actin)
thick and thin filaments aleternate with each other in a structure called
sarcomere
unit of contracation in a muscle cell
sarcomere
stimulated by an electrochemical signal from a nerve cell associated with the muscle fiber
contraction
for a muscle cell to contract, the sarcomere must shorten/elongate
shorten
molecular extension of myosin that temporarily binds to an actin filament next to it and through a change in conformation, bends, dragging the two filaments in opposite directions
myosin head
provides th energy for the contraction
ATP
are not the same, differ in structure and function
skeletal muscle fibers
skeletal muscle fibers contract at different speeds depending on their ability to split ___
ATP
skeletal muscle is classified into two broad types f
fast twitch
slow twitch
alters calcium currents, charge movement, and excitation-contraction coupling processes, highlighting its significant impact on muscle function and physiology.
glycerol
is added to muscles to facilitate muscle contraction by providing the necessary energy for the complex process of actin-myosin interaction and movement during muscle contractions
0.25% ATP in triple distilled water
alters the muscle’s response, resulting in a shrinkage of the muscle fibers. This indicates that the combination of these substances in distilled water influences muscle contraction differently than when ATP is used alone.
0.25% ATP + 0.05M KCI + 0.001 MgCl2 in dH2O
muscle fibers exhibit a response that differs from when ATP is present
0.05M KCI + 0.001 MgCl2
degree of contraction formula
initial length (mm) - contracted length (mm)
contraction % formula
degree of contraction (mm)/initial length (mm) *100
What differences do you see? What zones (or bands) have disappeared?
After the frog’s leg muscle fibers have contracted, the H zone and the I band have decreased in size but the A band remained the same. In a muscle, the H zone in the A band has only thick filaments and gets smaller when the muscle contracts. The I band, found outside the A band, has only thin filaments and also reduces in size during contraction. The A band, made up of both thick and thin filaments, doesn’t decrease in size during contraction. However, the A bands of different sarcomeres move closer together and eventually disappear. The disappearance of the bands can be associated with the shortening of the sarcomere and the overlapping of the thin and thick muscle filaments during contraction.
When ATP was applied in the absence of potassium and magnesium ions, what contraction was observed in the muscle fibers
little to no
When muscle fibers are flooded with potassium and magnesium ion-containing solutions that lack ATP, the muscle fibers exhibit a response characterized by
rigor contractions
refer to a state of continuous and sustained muscle contraction without relaxation, which occurs when the muscle is deprived of ATP
rigor contraction
provides the energy required for muscle contraction through breaking the bond between the myosin and actin, resulting in the myosin head to return to its initial position after completing a power stroke.
ATP
helps in the muscle contraction hyperemia, which is the increased blood flow to working muscles. An increase in extracellular K+ during muscle contractions is thought to be a vasodilatory signal contributing to exercise hyperemia.
potassium
affects the rate of calcium binding to various sites involved in muscle contraction regulation.
magnesium
are fatigue-resistant and are ideal for prolonged motions and postural control. They are aerobic and contain more myoglobin for oxygen transportation, making them red. Examples include lower leg and back muscles
slow twitch muscle
are larger, provide powerful forces but quickly fatigue, and need anaerobic respiration. They are paler in color because they have less myoglobin. An example of this would be the muscles in our eyelids that facilitate blinking.
fast twitch
intracellular/extracellular potassium contraction is much greater than its counterpart concentration
intracellular
intracellular ___ concentration is considerably less than its extracellular contcentration
sodium
hence steep ____ _____ exists for both cations
concentration gradients
change in ___ underlie the muscle cells and neurons ability to do work (contract or signal respectively in muscle cells)
voltage
occurs only if the muscle is stimualted with a stimulus of threshold or suprathreshold intesity
muscle contraction
minimum strength necessary to initiate a contraction
treshold stimulus
nerve that transmit a nerve impulse to the skeletam muscle
motor neuron
produce different kinds of contractions depending on the intensity and frequency of the stimulus applied
skeletal muscle
any record of muscle contraction
myogram
do not occur in the body but are worth demonstrating because they show the different phases of muscle contraction quite clearly
twitch contractions
study the demonstration of treshold stimulus (table)
Stimulus Strength
Contraction Strength
(Threshold, subthreshold, Maximal, submaximal)
1Threshold
2Threshold
3Threshold
4Threshold
5Threshold
6Submaximal
7Submaximal
8Submaximal
9Maximal
10Maximal
the period of a few ms for the chemical and physical events preceding actual contraction.
latent period
tension increases as action potential is spreading along the length of the muscle tissue
contraction period
muscle relaxes, relieves tension or comes back to its original length.
relaxation period
states that, once threshold is reached, a muscle will contract maximally, and that a subthreshold will not elicit a response
all or none
the addition of a second twitch, resulting in greater tension, and it results from stimulating the muscle before it has a chance to relax completely
sumation
prolonged contraction without relaxation and results from repeating stimulation before the muscle has a chance to relax at all.
tetanus
can be differentiated from quantal summation because the strength of stimulus remains the same in treppe, but increases in quantal summation
treppe
is the term used to describe the compounding effect of repeated muscle contractions in which a muscle fiber is activated prior to its complete relaxation following a contraction. As a result, more force is produced than could be produced by a single contraction.
summation
means that the effects of impulses received at the same place can add up if the impulses are received in close temporal succession.
temporal summation
efers to the ability of the muscles to exert various levels of force while maintaining continuous control over the intensity of contraction.
graded muscle contraction
efers to the activation of motor neurons and muscle fibers in a coordinated manner to generate varying levels of muscle force based on the task requirements and effort exerted
motor unit recruitment
also called the frequency-dependent activation or staircase phenomenon—is the progressive augmentation of muscle contraction force brought on by repetitive stimulation following a rest interval.
treppe effect
What was the effect of the rest period on the fatigued muscle? What is the physiologic basis for this reaction?
The rest interval duration between the contractions plays a role in alleviating muscle fatigue within the affected muscle groups according to Nogueira et al. (2012), the rest interval length directly impacts the rate of muscle fatigue recovery which means shorter rest intervals lead to greater fatigue while longer rest intervals promote faster recovery.
the heavier the load, the ____ the stretch of them uslce
heavier
A muscle can return to its original length when relaxed due to a quality of muscle tissue called
elasticity
the ability of a muscle to be stretched or extended.
extensibility
determined by multiplying the grams of the load lifted by the height (mm) with the results being expressed in gram-millimeter
amount of owrk
increase in the load is followed by the increased amount of ____
work done
when am uscle contracts withou t a load, or when the load is too heavy to be lifted, ___ mechanical work can be measured
no
interval of weights added
10 grams
study the values for the calculation of work performed by the muscle
+1
distance from the pivot to the muscle
AB
distance from pivot to writing tip
AC
distance from pivot to weight
AF
height of recorded contraction
CD
height of actual muscle contraction
BE
amount of work performed by the muscle may be calculated from the recorded height of each contraction and weight lifted
BE/AB = CD/AC or BE = AB/AC x CD
actual lifting force if there is a weight
AF/AB x Weight
refers to the ideal amount of weight or resistance used during a workout to achieve the desired effect, typically increased muscle strength or hypertrophy.
optimal load
